1. Field of the Invention
The present invention relates to multi-type air conditioner, and more particularly, to a method for controlling a multi-type air conditioner which enables to minimize stagnation of refrigerant at turned off indoor units during some of the indoor units are in operation for heating rooms, and reduce noise occurred when the stagnant refrigerant is removed.
2. Background of the Related Art
In general, the air conditioner is an apparatus for cooling or heating rooms, such as residential space, restaurant, office, and the like. Nowadays, for effective cooling/heating of a room space divided into a plurality of rooms, there has been ceaseless development of the multi-type air conditioner that can perform cooling or heating, or cooling and heating at the same time depending on an operation condition.
The multi-type air conditioner has a plurality of indoor units connected to one outdoor unit, so that only some of the indoor units perform cooling or heating according to user's requirement.
In this instance, in a case some of the indoor units of the multi-type air conditioner perform heating, even though the indoor units which perform heating is turned on, rest of the indoor units are turned off.
However, since the refrigerant is supplied from the outdoor unit to all of the indoor units of the multi-type air conditioner, the refrigerant is introduced into the turned off indoor units unnecessarily and stagnant therein as the heating is progressed.
The stagnant refrigerant at the turned off indoor units results in shortage of refrigerant circulating through the multi-type air conditioner, not only to reduce operation efficiency, but also elevate a discharge temperature of the refrigerant and reduce a discharge pressure, owing to a low flow rate of refrigerant in/out of the compressor.
Therefore, a control part of the multi-type air conditioner opens an expansion valve on the turned off indoor unit, to prevent stagnation of the refrigerant.
However, the uniform opening of the expansion valves at regular intervals by the control part of the related art multi-type air conditioner makes performance of proper operation control difficult.
Particularly, because a loud noise is occurred when the expansion valve is opened to discharge the refrigerant, if the expansion valve is opened periodically regardless of operation condition, to occur the noise periodically, product reliability drops, and complaints from users will result in.